As technology advances, electronic devices such as mobile phones, home appliances, personal computers (PC), personal digital assistants (PDA), liquid crystal displays (LCD) have changed to use a digital scheme, rather than an analog scheme, and thus, processing speeds thereof have increased, according to an increase in data throughput. Thus, USB 2.0, USB 3.0, and high definition multimedia interfaces (HDMI) have come into widespread use as high-speed signal transmission interfaces, and such interfaces have been used in a range of digital devices, such as personal computers and digital high-definition television sets.
Such high-speed interfaces employ a differential signal system therein, transmitting differential signals, for example, differential mode signals, using a pair of signal lines, in a manner different from a single-end transmission system having been commonly used for a long period of time. However, since digitized and high-speed electronic devices are sensitive to external stimulation, signal distortion due to high-frequency noise has often been caused.
As causes of the occurrence of such abnormal voltages and noise, a switching voltage generated in circuits, power noise included in a power supply voltage, unnecessary electromagnetic signals or electromagnetic noise, and the like may be present. As a means of preventing such an abnormal voltage and high-frequency noise from being introduced into circuits, a common mode filter (CMF) has been used.
In order to remove common mode noise affecting communications sensitivity in future mobile devices, common mode filters will be required to have ultra-wideband attenuation characteristics in a relatively wide communications frequency band as compared to a current communications frequency band.
A common mode filter having a shunt electrode structure has been used to secure such ultra-wideband attenuation characteristics, but increasing a frequency domain of an existing shunt structure has limitations.